Frequency diversity remote controlled initiation system

ABSTRACT

A blasting system includes a wireless link between a blast controller and a plurality of electronic detonators. Each detonator includes a respective electronic initiator and an explosive charge. Charge storage devices of the initiators are chargeable by a carrier of a first signal having a first frequency (f 1 ) in the order of 400 MHz-500 MHz and which is broadcasted by the blast controller. Each initiator further includes logic circuitry driven by a clock signal which is derived from the first signal and having a clock frequency of about 4 kHz, which is substantially less than the first frequency.

TECHNICAL FIELD

THIS invention relates to electric and electronic blasting systems formining applications, detonators and initiators therefor.

SUMMARY OF THE INVENTION

According to the invention there is provided a blasting systemcomprising a wireless link for broadcasting towards a plurality ofdetonators a first signal comprising a first frequency and wherein eachdetonator comprises logic circuitry driven by a second signal having asecond frequency which is substantially lower than the first frequency.

The second signal may be a clock signal which may be derived from thefirst signal.

The first signal may comprise a carrier signal having the firstfrequency. The first frequency may fall in the range 200 MHz to 100 GHz.The first frequency is preferably about 400 MHz to 500 MHz. The firstsignal may further comprise a data signal modulated on the carriersignal. Any suitable modulation technique such as amplitude modulation,frequency modulation, pulse-width modulation, pulse-code modulation etcmay be utilized.

Each detonator may comprise a charge storage device which is chargedwhile the detonators are energized utilizing the first signal. Thecharge storage device may comprise a capacitor. In other embodiments thecharge storage devices may be charged via a physical conductive linkfrom a common source of charge, such as a battery.

The clock signal may be derived by dividing the frequency of the firstsignal down by divider means. The clock frequency may be between 1 kHzand 15 kHz, typically between 4 kHz to 5 kHz.

The divider means may be common to at least some of the detonators andthe divider means may be connected to a receiver forming part of thewireless link as well as to said at least some of the detonators by aphysical conductive link.

In other embodiments the divider means may comprise a respective dividercircuit for each detonator.

Each detonator may comprise an electric or electronic initiatorcomprising a high frequency part and a low frequency part, the highfrequency part comprising an RF receiver stage, said charge storagedevice connected to the RF receiver stage and said respective dividercircuit.

The low frequency part may comprise a phase-locked loop and localoscillator connected to an output of said respective divider circuit andproviding the clock signal to the logic circuitry forming part of thelow frequency part.

An input of the logic circuitry may be connected via a data line to anoutput of a level detection circuit in the high frequency part. Thelogic circuitry may be programmable by delay time data in the datasignal to operate a switch of the initiator to cause charge on thecharge storage device to be dumped into a fuse of the detonator, a delaytime, which is associated with the delay time data, after a fire signal.

The divider means may divide the first frequency by about five orders,so that the frequency of the clock signal is in the order of 1 kHz-15kHz.

The high and low frequency parts may be integrated on a single chip.

In other embodiments, the high frequency and low frequency parts may besplit into separate first and second parts respectively and the outputof the divider circuit in the first part may be connected by a physicalconductive link to the second part. The first or high frequency part maybe located towards a mouth or collar of a blast hole wherein thedetonator is located, and the second part may be located towards abottom region of the hole.

The wireless link may be provided between a remote blast controllercomprising an RF transmitter and an antenna located in close proximityto the blast controller on the one hand and the plurality of detonatorson the other hand.

In other embodiments the wireless link may be provided between saidplurality of detonators and an RF transmitter located in closerproximity to the detonators. The antenna may be a line source, forexample the antenna may comprise a cable running the length of a longrelatively narrow blast site.

The RF transmitter may be connected to the blast controller by aphysical conductive link. Alternatively, a second wireless link may beprovided between the RF transmitter and the remote blast controller.

Also included within the scope of the present invention is a method ofoperating a blasting system comprising the steps of:

-   -   broadcasting a first high frequency RF signal to each of a        plurality of detonators; and    -   utilizing a second low frequency signal for driving logic        circuitry forming part of each detonator.

The second signal is preferably derived from the first signal bydividing down the frequency of the first signal.

Yet further included within the scope of the present invention is aninitiator for a detonator, the initiator comprising:-

-   -   a high frequency part comprising a radio frequency receiver        stage for receiving a first high frequency signal; and    -   a low frequency part comprising logic circuitry which is driven        by a second signal having a frequency which is lower than the        frequency of the first signal.

BRIEF DESCRIPTION OF THE ACCOMPANYING DIAGRAMS

The invention will now further be described, by way of example only,with reference to the accompanying diagrams wherein:

FIG. 1 is a basic block diagram of a first embodiment of an electronicblasting system according to the invention;

FIG. 2 is a block diagram of an electronic initiator according to theinvention and forming part of a detonator of the system in FIG. 1;

FIG. 3 is a basic block diagram of a second embodiment of the systemaccording to the invention;

FIG. 4 is a basic block diagram of a third embodiment of the systemaccording to the invention;

FIG. 5 is a basic block diagram of a fourth embodiment of the systemaccording to the invention; and

FIG. 6 is a basic block diagram of a fifth embodiment of the systemaccording to the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

A first embodiment of a blasting system according to the invention isgenerally designated by the reference numeral 10 in FIG. 1.

The system comprises a blast controller 12 comprising a radio frequencytransmitter 14 connected to an antenna 16. The transmitter, in use,broadcasts a first signal comprising digital data modulated on a carrier18 having a first high frequency f₁. The digital data is generated by adata generator 20 and intended for communications with and moreparticularly to program a plurality of electronic detonators formingpart of the system.

The system further comprises a plurality of similar electronicdetonators 22.1 to 22.n. Since the detonators are similar inconfiguration, only detonator 22.1 will be described in more detailhereinafter. The detonator 22.1 comprises an electronic initiator 24 andan explosive charge 26. The detonator 22.1 is located in one hole 28.1of a plurality of spaced blast holes 28.1 to 28.n. The initiator 24 isconnected via a lead conductor 30 to an antenna 32.

In FIG. 2, there is shown a more detailed block diagram of the initiator24. Antenna 32 is connected via lead conductor 30 to a radio frequency(RF) receiver stage comprising a rectifier 34. An output of therectifier 34 is connected to a charge storage device in the form of acapacitor 36, to energize or charge the capacitor with energy in thefirst signal. The output is also connected to level detection circuit38. The level detection circuit is connected to a divider circuit 40 fordividing down the high frequency carrier 18 of frequency f₁ to a signalhaving a lower frequency f₂. The signal with lower frequency f₂ is usedto drive a phase-locked loop circuit and local oscillator 42. Aresulting low frequency output signal s₂ (f₂) of the local oscillator isused as clock signal to drive logic circuitry 44. The logic circuitry 44drives a switch circuit 46 to connect a fuse 48 to the capacitor 36 viapower line 50, after a pre-programmed delay time associated with thedetonator. The delay time is typically programmed into the logiccircuitry 44 by delay time data modulated at a suitable rate on theaforementioned carrier signal and utilizing a unique pre-programmedaddress of the device. The various circuits 34 to 46 may be integratedon a single chip. These circuits derive electrical power from capacitor36, via power line 52. In some embodiments the carrier and data may bedivided down and in other embodiments only the carrier is divided down.

An output of level detection circuit 38 is connected via data line 54 toa data input 56 of logic circuitry 44. A comparator in logic circuitry44 recovers the digital data modulated on the carrier 18 and receivedvia the antenna in known manner. As stated hereinbefore, an example ofthe digital data is data relating to the aforementioned delay time andwhich data is utilized in known manner by the logic circuitry to causethe switch to connect the capacitor 36 to the fuse 48 at the end of therelevant delay time, following a common “fire” signal, for example.

The frequency of the carrier may be between 200 MHz and 100 GHz,typically 400 MHz. A divisor of the divider 40 is typically equal to10⁵, so that the frequency f₂ is in the order of 4 kHz. The frequency f₂may fall in the range 1 kHz to 15 kHz. The data may be modulated on thecarrier at a rate in the order of 100 MHz.

Hence, in use, the high frequency f₁ of the carrier is used to chargecapacitor 36, while the signal s₂ having a low frequency f₂ is used asclock signal for the logic circuitry 44. The logic circuitry whenoperating on a lower frequency f₂ is more power efficient than with ahigher frequency f₁.

In FIG. 3, there is shown a second embodiment of the system. Thecontroller 12 broadcasts the signal having carrier frequency f₁ to ahigh frequency part 60 of a split initiator 61. The high frequency part60 comprises a divider as hereinbefore described and a low frequencyoutput which is connected via a conductive physical link in the form ofnormal, low cost wires 62 to an input of a low frequency part 64 of theinitiator including at least the logic circuitry 44, switch and fuse.The high frequency part may in use be located in a mouth or collarregion of the blast hole and the low frequency part adjacent the charge26 towards a bottom region of the hole.

In the third embodiment 300 of the system shown in FIG. 4, the blastcontroller 12 is of split configuration. The data generator is housed ina first part 12.1 and the transmitter 14 forms part of a separate secondpart 12.2 which is connected via an extension cable 70 to the firstpart. The first and second parts are spaced a distance d₁ of typicallybetween 200 m and 3000 m from one another. The second part 12.2 isspaced a distance d₂ of typically in the order of 50 m from each of thedetonators 22.1 to 22.n in respective blast holes 28.1 to 28.n.

In FIG. 5, there is shown a blast controller 12 transmitting via adirectional antenna a communication signal comprising digital datamodulated on a high frequency carrier 18 of frequency f₁. A common andcentral divider 80 connected via a receiver to directional antenna 82divides the carrier frequency down to a low frequency f₂ of a signal s₂.The signal s₂ is transmitted via physical conductive link 84 todetonators 22.1 to 22.n in blast holes 28.1 to 28.n. This signal isutilized to energize the detonators and each detonator comprises aninitiator comprising a charge storage device, the required logiccircuitry, switch and fuse as hereinbefore described.

In FIG. 6, there is shown a fifth embodiment 90 of the system accordingto the invention. The blast controller 12 is of split configurationcomprising a first or master part 12.1 and a second slave part orrepeater part 12.2. The slave part 12.2 comprises a single antenna 92for communications with the master part via wireless link 93 and forcommunications with respective detonators 22.1 to 22.n also via arespective wireless link 95.1 to 95.n. The slave part 12.2 hencecomprises a transceiver 94 and single antenna 92 is connectable by anelectronically controllable switch 96 to either a receiver oftransceiver 94 cooperating with link 93 or a transmitter of thetransceiver for broadcasting a first high frequency signal to detonators28.1 to 28.n, as hereinbefore described.

In other embodiments the first signal 18 may not be utilized to energizethe detonators and may comprise a carrier having the first highfrequency and a data signal modulated on the carrier. The data signal isused to communicate with the detonators via the wireless link from aremote site 12. The data signal may hence comprise address data for anaddressed detonator and delay time data for that detonator ashereinbefore described. In these embodiments the detonators may compriserespective on-board power supplies or batteries. Alternatively, chargestorage devices in the form of capacitors on these detonators may becharged via a physical link such as link 84 shown in FIG. 5 from acommon source of charge such as a battery. Each detonator may stillcomprise an RF receiver stage for receiving the programming data via thewireless link. Accordingly the data integrity required on the physicallink would be reduced, since the physical link is utilized forenergizing the detonators and not for data communications. The steps ofcharging the detonators, programming the detonators via the RF link andprocessing by the detonators of the delay time data may be performedsequentially.

In yet other embodiments the first signal 18 may be utilized both toenergize the detonators as hereinbefore described and to communicatewith the detonators as hereinbefore described. In these embodiments, thesteps of charging the detonators and of programming the detonators maybe performed substantially concurrently, or sequentially.

1. A blasting system comprising a wireless link for broadcasting towardsa plurality of detonators a first signal comprising a first frequency;and wherein each detonator comprises logic circuitry driven by a secondsignal having a second frequency which is substantially lower than thefirst frequency.
 2. A system as claimed in claim 1 wherein the secondsignal is a clock signal which is derived from the first signal.
 3. Asystem as claimed in claim 1 wherein the first signal comprises acarrier having the first frequency and a data signal modulated on thecarrier for communicating with the detonators.
 4. A system as claimed inclaim 1 wherein each detonator comprises a respective charge storagedevice which is charged by energy in the first signal.
 5. A system asclaimed in claim 1 wherein each detonator comprises a respective chargestorage device which is charged from a source of charge connected to therespective charge storage device by a physical conductive link.
 6. Asystem as claimed in claim 4 wherein the respective charge storagedevice comprises a capacitor.
 7. A system as claimed in claim 1 whereinthe first frequency falls in a range between 200 MH and 100 GHz.
 8. Asystem as claimed in claim 7 wherein the first frequency is about 400MHz.
 9. A system as claimed in claim 2 wherein the clock signal isderived by dividing the first frequency down by divider means.
 10. Asystem as claimed in claim 9 wherein the first frequency is divided downfive orders of magnitude.
 11. A system as claimed in claim 9 wherein thedivider means is common to at east some of the detonators and whereinthe divider means is connected to a receiver forming part of thewireless link and to said at least some of the detonators by a physicalconductive link.
 12. A system as claimed in claim 9 wherein the dividermeans comprises a respective divider circuit for each of said pluralityof detonators.
 13. A system as claimed in claim 12 wherein eachdetonator comprises an electronic initiator comprising a high frequencypart and a low frequency part, the high frequency part comprising aradio frequency receiver stage, a charge storage device connected to thereceiver stage and said respective divider circuit.
 14. A system asclaimed in claim 13 wherein the low frequency part comprises aphase-locked loop and local oscillator connected to an output of saidrespective divider circuit and providing the clock signal to the logiccircuitry.
 15. A system as claimed in claim 14 wherein an input of thelogic circuitry is connected via a data line to an output of a leveldetection circuit in the high frequency part.
 16. A system as claimed inclaim 15 wherein the logic circuitry is programmable by a datamodulating signal of the first signal, to operate a switch of theinitiator to cause charge on the charge storage device to be dumped intoa fuse of the detonator.
 17. A system as claimed in claim 13 wherein thelow frequency and high frequency parts of the initiator are integratedon a single chip.
 18. A system as claimed in claim 13 wherein the highfrequency part and low frequency part are split and wherein an output ofthe high frequency part is connected by a physical conductive link to aninput of the low frequency part.
 19. A system as claimed in claim 1wherein the wireless link is provided between a remote blast controllercomprising an RF transmitter and an antenna located in close proximityto the blast controller on the one hand and the plurality of detonatorson the other hand.
 20. A system as claimed in claim 1 wherein thewireless link is provided between said plurality of detonators and an RFtransmitter located in close proximity to the detonators.
 21. A systemas claimed in claim 20 wherein the RF transmitter is connected to ablast controller by a physical conductive link.
 22. A system as claimedin claim 20 wherein a second wireless link is provided between the RFtransmitter and a remote blastcontroller.
 23. A method of operating ablasting system comprising the steps of: broadcasting a first highfrequency RF signal towards each of a plurality of detonators; andutilizing a second low frequency signal for driving logic circuitryforming part of each detonator.
 24. A method as claimed in claim 23wherein the second signal is derived from the first signal by dividingdown the frequency of the first signal.
 25. An initiator for adetonator, the initiator comprising: a high frequency part comprising aradio frequency receiver stage for receiving a first high frequencysignal; and a low frequency part comprising logic circuitry which isdriven by a second signal having a frequency which is lower than thefrequency of the first signal.